NO149968B - ADDITIVE FOR LUBRICANTS AND LUBRICANTS CONTAINING THE ADDITIVE - Google Patents

Abstract

A lubricating oil additive having both viscosity index improving and dispersing properties is a polyisobutylene succinimide derived from a polyisobutylene having a weight average molecular weight of at least 10,000 and having a molar ratio of amine to acid or anhydride groups of less than 1: 1. The use of such molar ratios promotes the viscosity index improving properties by improving the ratio of viscosity to temperature.

Description

The present invention relates to an additive

for lubricants and lubricants containing such an additive.

It is known that medium to high molecular weight polyisobutylenes, e.g. weight average molecular weight of over 7000,

act as viscosity index improvers. It is also

known that polyisobutylenes can be converted into detergent-dispersant additives for lubricants and other products. Polyisobutylene succinimides are thus known, but the polyisobutylenes used for the production of succinimides normally have a lower molecular weight, e.g. a weight average mole-

cooling weight of 1000-7000.

It has been suggested that polyisobutylenes with a higher molecular weight can also be used for the production of polyisobutylene succinimides, but in practice this is not an entirely simple matter. Polyisobutylene succinimides are formed by a two-stage reaction. In the first step, polyisobutylene or chlorinated polyisobutylene is reacted with maleic acid or maleic anhydride and in the second step the resulting acid or anhydride is reacted with an amine. There is only one reactive group in polyisobutylene at the end of each molecule so that as the molecular weight of the polyisobutylene material increases, the ratio of acid or anhydride groups to isobutylene groups decreases. Furthermore, the ease of reactivity between the polyisobutylene compound and the maleic acid or anhydride decreases as the molecular weight of the polyisobutylene increases.

Due to these difficulties, it has been concluded

with little gain in converting high molecular weight polyisobutylenes into succinimides. In US Patent No. 4,169.C63

specified e.g. following:

"When the polymer has only 50 carbon atoms, sufficient dispersing sites may be available only through the single terminal double bond. However, when the polymer has over 500 carbon atoms as necessary for it to provide some viscosity-enhancing properties,

the individual terminal double bond will not be

extensive and a difficult "derivitisation" method is neces-

necessary to achieve sufficient dispersibility."

It has now been found that useful high molecular weight polyisobutylene succinimides can be obtained provided certain conditions are observed. Such products have been found to have better viscosity/temperature characteristics than the high molecular weight polyisobutylene starting material and also to have useful dispersing properties.

According to the present invention, it is provided

an additive for lubricants comprising a polyisobutylene succinimide, and this additive is characterized in that the polyisobutylene succinimide is produced by reacting a polyisobutylene succinic acid, or a polyisobutylene succinic anhydride derived from a polyisobutylene with a weight average molecular weight of from 25,000 to 200,000, with an alkylene diamine or an alkylene polyamine. quantity ratio that the molar ratio of amine groups to acid or anhydride groups is from 0.4:1 to 0.1:1.

A lubricant is also provided and it is characterized by the fact that it comprises a distillate or light lubricating oil fraction derived from petroleum containing 1-20% by weight of the above-mentioned additive.

By the term "lubricant" is meant any product that may need to be improved in terms of viscosity index. It thus includes the normal vehicle and industrial lubricants and also transmission, traction and hydraulic fluids.

The lubricant may be an ester or a hydrocarbon lubricant or a mixture. The term hydrocarbon lubricant includes synthetic hydrocarbons, e.g. those produced by polymerization of olefins, as well as petroleum fractions that boil above 300°C, the latter being preferred. The designation thus includes all the normal distillate fractions or white oil lubricating fractions derived from petroleum.

For effective viscosity index improving properties, the polyisobutylene should have an average molecular weight of at least 10,000. It can generally be said that the higher the molecular weight the better, the limitation being the practical difficulties in the polymerization step because increased polymerization is promoted at lower temperatures. The weight average molecular weight is preferably from 40,000 to 200,000.

The ratio between weight-average molecular weight and number-average molecular weight Mw can be from 1 to 6.

M~

n

Suitable polyisobutylenes are those with the trade name "Hyvis", especially the qualities "Hyvis 7000/45, 50H and 58H"

(supplied as solutions in mineral oil).

The reaction between the polyisobutylene or the chlorinated polyisobutylene and the maleic acid or anhydride to form the polyisobutylene succinic acid or anhydride can be carried out in a known manner, but taking into account conditions that promote the reaction, because, as previously mentioned, the reaction becomes more difficult as the molecular weight of the polyisobutylene material increases.

The broad reaction conditions can be 150-250°C

at atmospheric pressure or elevated pressure for 4-48 hours depending on the molecular weight of the polyethylene starting material and the desired conversion. The reaction, which may be catalytic or non-catalytic, may be carried out in the presence of antioxidants or other stabilizers to reduce the formation of unwanted resinous by-product and minimize thermal degradation of the polyisobutylene. The reaction is carried out using molar ratios between maleic anhydride and polyisobutylene in the range from 30.0:1.0 to 1.0:1.0 and the reaction is favored by increasing the maleic anhydride:polyisobutylene molar ratio. Conversion levels for high molecular weight polyisobutylenes can be promoted by reacting chlorinated polyisobutylene with maleic anhydride or by reacting maleic anhydride with polyisobutylene in the presence of chlorine. The polyisobutylene used for the reaction can be dissolved in a suitable solvent, e.g. a mineral oil fraction, especially a lubricating oil fraction, to obtain a material of suitable viscosity for storage, pumping and general handling.

It is theoretically possible to use other unsaturated acids or acid anhydrides besides maleic acid or maleic anhydride, but there has been little commercial use of other materials.

The polyisobutylene acid or acid anhydride is then reacted with an amine. It has been found that this reaction proceeds rather easily even with high molecular weight polyisobutylenes and is therefore not a critical reaction. The polyisobutylene acid or acid anhydride dissolved in a suitable solvent, e.g. toluene, can be reacted with the amide at temperatures of 50-150°C (e.g. under reflux) for a period of

1-12 hours.

As is known, one can theoretically use a number of different amines with the general formula:

where R and can be hydrogen, hydrocarbon, amino-substituted hydrocarbon, hydroxy-hydrocarbon or oxy-hydrocarbon. To promote the production of succinimides with a molar ratio of amine to acid or anhydride groups of from 0.4:1 to 0.1:1, the amines should have at least two reactive hydrogen atoms and should preferably be di- or poly -amines. The particularly preferred amines are thus the (poly)alkylene polyamines. Examples of such polyamines are ethylenediamine and the polyethylene polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine and pentaethylenehexamine.

The molar ratios between amine and acid or anhydride groups must be calculated based on the amine used to form the succinimide and the acid or anhydride groups in the polyisobutylene succinic acid or anhydride.

Without being bound by theory, it is suggested that the use of the indicated molar ratio of amine to acid or anhydride groups results in the formation of bis-succinimides or in the case of polyamines, possibly products with three or more polyisobutylene succinic acid radicals combined with each amine. Nevertheless, whatever the theory, experimental results have shown that the correct choice of the molar ratio between amine and acid or anhydride groups is essential for obtaining the improved viscosity/temperature properties and, when the polyamine is tetraethylenepentamine, that the optimum molar ratio is 0.25:1.

With regard to the acid or anhydride groups, as mentioned above, there may be incomplete conversion of the polyisobutylene to polyisobutylene succinic anhydride and this should be taken into account, e.g. by determining the PIBSA number to indicate the degree of conversion.

The amount of polyisobutylene succinimide added to a lubricant will normally be in the range of 1-20% by weight (unless it is used in conjunction with another VI improver when less can be used), the better viscosity/temperature properties being used either to reduce the amount of VI improver required for a given grade, or to improve the grade for a given additive level.

The better viscosity/temperature properties, compared to the unmodified polyisobutylene starting material, are evident in that the present products provide oil blends with higher high temperature viscosities (100°C and 40°C) with either a lower low temperature viscosity (-18°C) or alternatively without a corresponding increase in the low-temperature viscosity (-18°C).

The lubricant may contain other conventional additives, e.g. anti-oxidants, EP and anti-wear agents, dyes, pour-point depressants, anti-corrosion agents and other VI improvers. The lubricant may also contain further detergent/dispersing additives (e.g. a low molecular weight polyisobutylene succinimide) depending on the level of detergent/surface activity/dispersibility required and the degree of surface activity/dispersibility provided by the product according to the invention.

The invention is illustrated by the following examples.

Examples 1-4

Production of polyisobutylene succinic anhydrides (PIBSA)

Polyisobutylenes with weight average molecular weights of 15,000, 27,000 and 51,000 (marketed under the trade name "Hyvis" as respectively "Hyvis 2000", "Hyvis 7000" and "Hyvis 58H"), were reacted with maleic anhydride. The polyisobutylenes were dissolved in a lubricating oil with a viscosity of 30 cSt at 38°C and a viscosity index of 100 in an amount such that a solution viscosity of 1000 cSt at 100°C was obtained.

The polyisobutylenes were reacted with excess maleic anhydride in a reaction flask with stirrers for 24 hours at 215-220°C. At the end of the reaction period, the crude product was dissolved in n-hexane (about 30% based on reactor feed)

and filtered through "Super-cel" to remove the insoluble resinous by-product and most of the excess maleic anhydride. The filtrate was stripped at 80°C/100 mbar to remove hexane and then at 180°C/10 mbar to remove the last traces of maleic anhydride.

The details of the preparations are given in table 1 below and the analytical data for the reaction products in table 2.

Examples 3 and 4 were carried out in the presence of 1.0% by weight

"Irganox 1010" to minimize thermal degradation of the polymer.

Table 2 shows that the relatively low conversions to

PIBSA was obtained despite the use of MA:polyisobutylene-

ratios of up to 20:1.

Examples 5-8

Preparation of polyisobutylene succinimides

The anhydride products in examples 1-4 were converted to polyisobutylene succinimides by reaction with tetraethylenepentamine.

Tetraethylenepentamine in toluene (45 mL) was added rapidly with stirring to polyisobutylene succinic anhydride in toluene (5 mL). The solution was refluxed for 6 hours, cooled and then stripped in a rotating film evaporator at an elevated temperature (100°C) and a reduced pressure (3 mm Hg) to obtain the polyisobutylene succinimide as a viscous liquid. With regard to quantities, reference is made to table 3 below.

Example 9

Viscosity test

The succinimide product of Example 7 was incorporated into a lubricating oil and compared to the unmodified polyisobutylene starting material dissolved in lubricating oil for viscosity/temperature performance.

The results are shown in table 4 below.

When comparing column 1 with column 3 and column 2 with column 4, it appears that the oils containing the succinimide products according to the invention had higher viscosities at 40°C and 100°C than the oils containing the unmodified polyisobutylene, but that "Cold cranking" -the viscosities at -17.8°C were similar.

Example 10

We scocity test

Example 9 was repeated using the succinimide product from Example 8 and the corresponding unmodified polyisobutylene. The products were dissolved in a mixture of lubricating oils so that viscosities corresponding to a 20W/50 type specification were achieved.

The results are shown in table 5 below.

The results are similar to those of Example 9, with the oils containing the succinimide product having higher 40°C and 100°C viscosities, and, in this case, lower -17.8°C viscosities.

Example 11

Example 10 was repeated using a lubricating oil which gave viscosities corresponding to a "15W/50" type specification.

The results, similar to those in example 10, are shown in table 6 below.

Example 12

A variety of polyisobutylene succinimides were formed using different molar ratios of amine to anhydride.

The starting polyisobutylene had a weight average molecular weight of 51,000 and the trade name "Hyvis".

This polyisobutylene was converted to polyisobutylene succinic anhydride using the technique described in Example 4. The conversion of polyisobutylene was 21% and the PIBSA number of the product was 3.0 mg KOH g <1>.

Quantities of this anhydride product were reacted with tetraethylenepentamine at various amine:anhydride molar ratios using the technique described in Example 8. The molar ratios, amounts of reactants and yield of succinimide product are given in Table 7 below.

Each of the succinimides was dissolved in lubricating oil and the viscosities of the oil determined at 100°C, 40°C and -18°C.

The succinimides were used in the form of 31% by weight solutions in a mineral oil (viscosity 30 cSt at 38°C; viscosity index 100). These solutions were then mixed with additional lubricating oil (a 75:25 mixture of the above oil and an oil with 95 cSt at 38°C and VI 95) to obtain oils containing 12% by weight, 9% by weight and 6% by weight -% polymer.

Using the same 75:25 blend of oils,

oils containing 12%, 9% and 6% of the starting polyisobutylene and the polyisobutylene succinic anhydride were also produced. The viscosities of these oils were also determined at 100°C,

40°C and -18°C.

The results are shown in the accompanying figures 1-3 which show graphical representations where the viscosity is plotted against the anhydride:amine molar ratio at three different temperatures.

In the graphical representations, the viscosities for the mixtures containing polyisobutylene or polyisobutylene succinic anhydride are shown as straight dashed lines which in reality constitute baselines. Compared to these baselines, the blends containing the polyisobutylene succinimides had higher viscosities at 100°C and 40°C and lower viscosities at -18°C. The viscosity at -18°C was not affected by the anhydride:amine ratio, but at 100°C and 40°C the graphs show an increasing viscosity as the ratio falls below 1:1 with a maximum at 1:0.25.

Example 13

Dispersibility test

The polyisobutylene starting materials, the anhydride products of Examples 1-4 and the succinimide products of Examples 5-8 were examined for dispersibility using a spot dispersibility test.

In this test, 4 g of additive was dissolved in 96 g of mixed base lubricating oils (70% w/w "BG 30/100", 30% w/w "95/95"). 2 g of carbon (250 micron M.T. carbon black) was dispersed in the additive oil solution using an ultrasonic probe with a power of 150 Watts for 5 minutes. Upon cooling to room temperature, 3 drops of the test solution were placed in spots on the center of a filter paper ("Whatman 41", ash-free). The papers were left on a clean, flat surface for 24 hours at room temperature and then the areas with carbon stain and oil stain were calculated from measuring the diameters of the stains (average of two measurements taken perpendicularly).

The relative dispersibility was calculated as a percent staining from:

The results are shown in table 8 below.

Table 8 shows that while the unmodified polyisobutylene and polyisobutylene succinic anhydrides had poor dispersing properties, the polyisobutylene succinimides had significant dispersing properties even when the polyisobutylene starting material had a molecular weight as high as 51,000.

Example 14

A variety of polyisobutylene succinimides were formed using different amine to anhydride molar ratios.

The starting polyisobutylene had a weight average molecular weight of 27,000 and had the trade name "Hyvis 7000". This polyisobutylene was converted into a succinic anhydride using the technique used in the above

example 4.

Quantities of the succinic anhydride were reacted with diethylenetriamine at various ratios of amine to anhydride.

Each succinimide was dissolved in a mineral oil (viscosity

30 cST and 38°C; viscosity index 100) to obtain oil end products containing 12% by weight of the additive.

A 12% solution of the polyisobutylene succinic anhydride i

the same lubricating oil was also produced. The viscosities of these oils at 100°C, 40°C and -18°C were then determined.

The results are shown in the accompanying fig. 4-6,

which represent plots of viscosity versus molar ratio of anhydride to amine at the three different temperatures. The results show the viscosity peaks over the same anhydride:amine ratio, ie 1:0.4 to 1:0.1 at 40°C and 100°C, as seen in the results of Example 12, Fig. 1-3. The example thus demonstrates that the improved properties of the polyisobutylene succinimides according to the invention can be achieved with an amine different from tetraethylenepentamine.

Claims (2)

1. Additive for lubricants comprising a polyisobutylene succinimide, characterized in that the polyisobutylene succinimide is produced by reacting a polyisobutylene succinic acid, or a polyisobutylene succinic anhydride derived from a polyisobutylene with a weight average molecular weight from 25,000 to 200,000, with an alkylene diamine or an alkylene polyamine in such a ratio that the molar ratio of amine groups to acid or anhydride groups is from 0.4:1 to 0.1:1. 2. Lubricant, characterized in that it comprises a distillate or light lubricating oil fraction derived from petroleum containing 1-20% by weight of the additive according to claim 1.